These Cubesats Could Use Plasma Thrusters to Leave Our Solar System

Cubesats are all the rage these days: they’re usually inexpensive and quick to build and they can tag along on launches already scheduled for other things. We think of cubesats as being almost “disposable” satellites – tiny spacecraft that go into Earth orbit for a short time, do their science and then burn up harmlessly in Earth’s atmosphere. But a team of scientists have a more long-term, long-distance plan for their cubesats. Benjamin Longmier and James Cutler from the University of Michigan want to build cubesats that have tiny plasma thruster engines that could propel them into deep space, maybe even interstellar space.

They have a vision of their plasma-thruster cubesat waving as it speeds past the Voyager spacecraft at the edge of our Solar System.

They are working on what they call the CubeSat Ambipolar Thruster (CAT), a new plasma propulsion system. This thruster technology doesn’t exist all in one piece yet, but Longmeir and Cutler said they could put it together in months, with just a little funding. The CAT plasma thruster will propel a 5kg satellite into deep space, far beyond Earth orbit, at 1/1000th the cost of previous missions.

They’ve begun a $200,000 Kickstarter campaign to help fund their project. Their ideas of what these thruster propelled cubesats could do are mind-bogglingly exciting: flying through the plumes of Enceladus to look for life, studying and tagging asteroids, formation flying through Earth’s magnetosphere to learn more about solar flares and the aurora or just an interplanetary message in a bottle lasting for hundreds of millions of years in orbit around the Sun.

They think they can get a satellite up and flying within 18 months.

“The traditional funding process starts with some seed data, a large government grant and a large number of milestones and gates to go through,” said Longmier in a press release from the University of Michigan. “We’d like to leverage Kickstarter funds to compress that timeline and go from initial seed data to flight in about 18 months, a much faster time scale than is possible with traditional grants.”

The cubesats would be about as big as a loaf of bread and the thrusters – the first of its kind — would use superheated plasma directed through a magnetic field to propel the CubeSat. The duo says that with this technology, exploring interplanetary space and eventually other planets would become faster and cheaper than ever before.

While plasma rockets have been used before, they’ve only been used on big spacecraft like Deep Space 1 and DAWN. Longmier and Cutler are miniaturizing the system. Most of the thruster components have been built and have been tested individually, but they need help through Kickstarter to assemble everything into one compact thruster unit for testing the integrated components in the lab, then in Earth orbit, and then interplanetary space.

One satellite is more efficient and cheaper than 100 smaller ones that has the same equivalent functionality as the big one. 100 smaller ones have more surface exposed to the vacuum than the big one. They all need their own RCS thrusters, cooling systems…. They all need to be tested independently…

It is the same as saying: replace all buses by 50 cars and claiming that 50 cars would be cheaper than a bus.

A mission through the ice plums of Enceladus would be something! Though it may need a tiny 20 watt RTG for the job. However, thanks the low mass of a cube sat, it could be sent on a direct trajectory to Saturn with a small launch vehicle and use its plasma thruster to break into orbit.

Cassini has a 4 meter diameter radio dish and at least 700 Watt from 33 kg plutonium. And access to the Deep Space Network on Earth. But that stuff is maybe unnecessary, and an ordinary cell phone would’ve worked just as well?

Unless a cubesat returns to Earth orbit for communication, it has no business going far away. Communcation via Cassini might require maneuvering and a conventional rocket engine for that purpose. Also, protection against radiation outside of about 400 km from Earth might multiply its cost since all electronics must be specially designed. And then you have your ordinary $100 million+ interplanetary probe.

How long time would it take for its plasma engine to reach Saturn? 10 years? 20 years? Its instruments will be obscolete when it arrives. A direct launch to Saturn would require a dedicated launch vehicle, since such a trajectory is not useful for any other payload. So add another $100 million to the budget.

Cassini’s radio dish transmits 20 watts of power. Not 700 watts. With a super-light-weight, structureless high gain antenna, a deep space cube sat powered by a 25 watt RTG would be receivable by our current deep space network. A laser transmitter, which needs development with accurate pointing, would be more efficient and thus use less power and be much lighter than a radio based system. I believe Planetary Resources want to use this technology for their own spacecraft.

If this is meant to be serious yet cost effective astrobiology mission, the electronics would definitely need to be specially designed anyway. I imagine it would need an aerojell wafer like StarDust to capture the ice particles, a particle plucker, a microscope, a protein detector chip, a spectometer and four cameras. However, using cellphone electronics could be protected by a titanium casing and surrounded by its propellant. There is only one way to find out.

A direct launch to Saturn should not require a dedicated launch vehicle. With an assumed mass of 14 kg, it could piggyback the upper stage of the Falcon Heavy as a tertiary payload. It would still take the probe maybe about 5 years to reach Saturn. It would only use its plasma thruster to spiral down to orbit Enceladus and sample the plumes moving as slow as possible. This could be an 8 year mission.

It would definitely not be a $100 million dollar mission, [unless inflation catches up ;c) ] But more realistically, a budget of $35 million may be necessary. Compared to other proposals this would be a very, very cost effective mission.

Before panning that, we need a good series of successful kickstarter programs like the one described above missions to make people and the agencies take the technology more seriously. This kickstarter is to demonstrate that cubestats can truly shine beyond Earth orbit. Miniaturization has made the computer and cellphone industry thrive and become common. This should be the same with deep-spacecraft to explore the Solar system.

Lasers will have trouble with bandwidth, 10 watt in a 10 arcsecond-wide beam are on the order of 10^-15 W/m^2 or several thousands of photons per square meter per second and the hard limit for the bitrate would several kbps. Pointing problems aside, it would be hard to get narrower beam or much higher power (but unfoldable super-thin film solar cells would work even at Saturn’s distance) No HDTV for deep space.

Only 20 W from Saturn? Then that problem is much smaller than I thought.

It anyway seems to me that the cubesat concept is incompatible with interplanetary travel. When the costs increase to get out there, one might as well use a more expensive probe concept, like turning it into an orbiter. Some challenges you don’t have in LEO are:

Radiation protection, one technique is to use 3+ of electronic components, getting big for the cube concept. Energy, small solar panels won’t do too far out. Travel time, ages technology onboard and worsens the problems with radiation and energy. Trajectory, most launches are to geostationary orbit, some comprimise with cost or travel time must be made to piggyback to Saturn on a launch like that.

Of course, the costs for all above will go down and one day work with low cost satellites, but today it would be a bit like shipping iron ore with airplanes.

If you send a series of smaller cubes spread out, then they can act as a relay for each other. Also because hey are spread out, they have a wider range of sensors spread over a bigger area. The hard part is to reconstruct the data because you need to know the exact position of every cube that you cannot control that easily.

I don’t know what the Enceladus mission idea came from. The Kickstarter page describes much more realistic exploration of the technology, and the early interstellar probe demo project has the probe dying well before it can symbolically “wave” passing at Voyager’s distances.

Incidentally one of the envisioned uses of enhanced cube sats, lets emBorgen them to “cube crafts”, is to expand DSN type functions with a deep space internet, around Earth at first. If they can swing the necessary lifetimes for that, cube crafts could go as far as their small solar panels takes them.

People are piggy-backing crafts, mostly landers, so local survey nets may be a way to complement future interplanetary missions. (Needs cube crafts piggy-backing within a rad shield, which perhaps the main mission fuel tanks can provide.)

Solving the power problem to get some source that could stand the short time unshielded electronics can work is a must.

It seems to me that the real usefulness of something like this would be in giving more flexibility to orbits. Cube sats equipped with such a thruster could launch into whatever orbit the primary payload required but then move to higher or lower orbits optimal for their missions. Multiple cube sats destined for vastly different orbits could be launched together from a single faring. No need to compromise.

I have the feeling that there is a dangerous trend in space exploration. The disposable/mass production logic that completely changed our way of living on earth and that destroyed the environment is now conquering the space sector. I’m all for space exploration (it is one of our primary tasks as an evolving species I think) but we must be careful about all these things we put into space. Not only for space debris but also resource-wise. All these special materials we lift off can never be recuperated. I know it is tiny if you compare it to the reserves on earth but we have to tackle space with a bit more care then we tackled the industrialisation of society. We have experience in these thinks (polluting and throwing things away) so I would expect that we learn from it but it appears that our urge to expand – whatever the cost – is too strong to stop.

Do you know how large Earth compared to the mass of these satellites? The drain isn’t tiny, it is insignificant.

And I don’t know why anyone worries about leakage.

– The unavoidable natural process of net sum of material leaking into space, mostly atmosphere volatiles, and transported here, mostly interplanetary dust and asteroid rock, is perhaps negative but we gain in the “special materials”.

– Several of the first space commercials are set to recuperate asteroid material, specifically for space construction.

As we all know, industry and society is self regulating. See how much cleaner the cities and the industry are compared to early stages. I wouldn’t worry about long term results with that historical background.

Finally, expansion isn’t an undefined ‘cost’, it is a way to live. As our biosphere discovered 4 billion years ago. We could have worse teachers, with a worse track record.

I was generalizing about all kinds of space-related activities of humanity. The satellites of these articles are indeed insignificant and even all satelites/debris is insignificant but I have a problem about the principle. The mass and volume of a cigarette is also insignificant but throwing it onto the streets is simply an imoral act. I hope you understand my position now. Yes, using this technology for cleanup is a great idea. And as I stated in the reply to Olaf2 I am pro-progress (but I would recommend a more careful approach).

Yes I hope we will remain self-regulating and hopefully improve on that field.

Are you saying that the amount of ‘special materials’ on earth is increasing over time because of space dust entering our atmosphere? Or the other way around? I don’t know so I’m just curious.

I’d answer that yes, human access to ‘special materials’ is increasing exponentially all the time. Thanks to new extraction technologies et cetera. Google “japan rare earth minerals”. Or “frozen methan hydrates”, for example. There are good news out there. At times, now and then throughout history, some believe that resources might be depleted. But I can’t think of any examples where that proposed phenomenon has actually occured.

Thanks. If you look it at it that way then I must agree. But we keep finding new materials/reserves because of the fact that they are becoming more rare (because we consume them rather inefficiently) and thus it justifies the higher costs for exploring and recovering them.

I’m not against progress and technological improvement. I’m worried about the inability of humans to cope with it. I have the feeling that the technological progress is happening too fast, our behavior cannot follow.

We must cope with technology but we have to learn it better. It is going too fast and our moral capacity is far behind our technological capacity in my opinion. We simply have to learn how we must use and cope with the magnificent tools we create.

I actually do think you are hostile against technology progress after all. If I may speculate, I think you mask it for yourself, behind an irrational emotion of fear. Space exploration increases our security and prosperity, when conducted according to what can be balanced by demand and supply, i.e. by what people want and what people can do. That’s what we’ve seen thus far. Relax, the fear is unwarranted. And certainly doesn’t come from economical, resource efficient little cubesats! Or do you propose inefficient satellites in order to make them more expensive and less demanded?

If I may speculate too, I would say that most peoples here (including you) believe in the ‘technological fix’, that our progress in technology and ingenuity will cure most if not all of our problems. It partially justifies our need to continually invent new stuff but it also makes us believe that we do not have to improve/change ourselves morally. That is the point I would like to make. I don’t want to sound negative/offensive, I am only concerned.

Technological progress can make things more sustainable, like these new propulsion systems that are more efficient. But it only delays the need to change our attitude. It is not THE permanent solution. That is how I see it.

I fear technological progress that can lead to more problems instead of solving them. Cheaper stuff means more production and consumption and thus more damage to our environment. But I don’t fear good progress like this new propulsion system. More efficient satellites? Yes, nice. But more of them? No.

Anyway, it is an interesting topic to discuss about but I’m going off topic, sorry for that!

Your fear of morality failing to keep up with
technological development is unfounded. Simply put, morals develop from experience,
not out of thin air. Because of this it’s simply not possible for a
moral to develop in advance of its cause (ie, social or technological change).

Keep in mind that while most humans are born with an innate set of behaviours, morals as you know them are things we learn after birth – things we developed. You can think of morals as a form of cultural technology we built over vast periods of time and continue to advance.

Because of this, improvements in our morality have come about as a *result* of technological and social change; they don’t precede them. Morals necessarily follow from changes in our society; they don’t cause such evolution themselves, but come after.

Yes, true. But the gap between experience and moral evolution seems to be too long in my opinion. And we never have the tendency to avoid something despite our long experience with new technological inventions (giving me the feeling that our learning process isn’t working well).

All experience of technology thus far has been a triumph. The only threats against progress are political or religious. Like a “moral” which downplays the value of humanity and irrationally fears some “end of resources”. It has already been pointed out here that the environment is getter better and better in many ways. We can afford that thanks to our increased production. We can use more and more dead mineral and don’t need to rely so heavily on animals and plants, the wildlife can be left alone. The area of food crop growing land has decreased last 50 years inspite of population growth, thanks to new technologies being mass produced. 12 hours around the world in an airplane needs less resopurces than 6 month in a steam ship.

I was referring to the mass-production tendency in the space industry. It is not because it is getting cheaper that we have to produce more. More production means more waste (orbital debris), less remaining resources (and thus getting more expensive) and more damage to our environment (space or on earth).

It is not happening too fast, it is happening too slow.
Better technology means more efficient rockets, more efficient satellites, better GPS satellites, better weather satellites…. The technology that is invested in space technology also means better materials, better cars and less dependency on metals, but more and more carbon nano tubes.

Hello, Saturn System Traffic Control. Our collision control just laser incinerated another one of those pesky cube sats left over from those 21st century morons. When is somebody going to do something about this annoying hazard?

Thanks for the laser info. I’d love to know more. Indeed, solar cells are becoming more and more viable in the outer solar system recently. First we have Juno on its way to Jupiter, and JUICE in the planning stage. I also remember reading a pdf about a solar powered relay for two Saturn decent probes. I’m not sure about its power budget. Though a PV system could reduce the overall cost of my imaginary Enceladus astrobiology cubesat. We’ll call it EAC. I calculated based on Curiosity’s MMRTG, EAC would need two GPHS modules for 31 watts of electricity of the start of the mission. I have no idea how much a mini MMRTG would cost over a PV power source. Though by dividing Curiosity’s power source, assuming 2.8 w/kg, EAC’s RTG would weigh about 11 kg. About 24.2 lbs. Yeahh, not exactly cube sat material and would be a big chunk of my earlier guesstimate. There could be ways to design a lighter or more efficient RTG, but I wonder how it would compare with a solar powered version, assisted by batteries. I have no means or resources to compare the two systems, but it would be really neat to see the cost, weight, and power differences.

Indeed. Plasma drives are so awesomely efficient. I did play with idea of a sample return mission with Enceladus. It would take a while for the round trip! 😉

I agree, perhaps smaller, more efficient,comparatively bite sized and narrow mission focused spaceprobes may be easier to swallow for government agencies these days and maybe a few decades to come. There are grand mission plans that simply don’t get the same support as they used to. We might not see another Cassini styled spacecraft orbiting Saturn until the late 2030’s. Though deep space CubeProbes, not bristling with as many instruments, could take up the slack. I agree, it’s better than nothing. And seeing clear pictures of Saturn and Neptune from little CubeProbes would be quite something and a BIG achievement, indeed.

oTay, so where do I sign up? send my employment application? Heck, I’d work for free to get involved with something like this! I’ve always thought that the way to explore the Moon, Mars and beyond, would be to send armadas of mini rovers and surface labs, and these guys looks like they are close to economically doing that! I like!

Actually there would little worry about. An imagined Cloud City would be floating 50 km (31 mi) above the surface – a region which is the most Earth-like place in the solar system. Pretty much sea-level pressure and room temperature. Breathing air would function as a lifting gas, and since pressures between the CO2 atmosphere and breathable interior would be almost equivalent, there wouldn’t be an explosive rupture if membrane puncture occurred. The thick atmosphere would block a lot of radiation. It’s much nicer than the surface, with bright, white skies. 🙂

Well yeah the idea sounds great in principle , but what would stop such a city from collapsing into Venus’s gravity well? If pigs could fly , then yeah why not a city with wings . But the fact is that keeping the thing from falling into Venus’s insanely dense lower atmosphere with Sulphuric acid clouds is going to require a LOT of energy.
We should just wait for the recent developments in magnetic shielding to pan out , then its just a matter of time before Humans can spread out into the belt , where resources are easy to get to and the radiation less intense.

Certainly you have heard of that old fangled, atmospheric, gravity defying apparatus known as… the balloon? (^.^) Notice I wrote that breathable air is a “lifting gas” in a CO2 atmsophere, and a decent one, too. Cited here:

“”Since air is a lifting gas on Venus: the entire lifting envelope of an aerostat can be breathable gas,allowing the full volume of the aerostat to be habitable volume. For comparison, on Earth, helium lifts about one kg per cubic meter, so a given volume of air on Venus will lift about half as much as the same volume of helium will lift on Earth.””–Geoffrey A. Landis, NASA Glenn Research Center.

In a dense CO2 atmosphere with sea-level pressures, (which would provide great protection against cosmic radiation) the air you breathe would help keep an imagined Cloud City aloft. According to Landis, a two-kilometer diameter envelope of breathing air would lift 6 MILLION TONS.

“So, if the settlement is contained in an envelope containing oxygen and nitrogen the size of a modest city, the amount of mass which can be lifted will be, in fact, large enough that it could also hold the mass of a modest city. The result would be an environment as spacious as a typical city.” – Landis, Pg.4

After its pressurized lifting-gas tanks have inflated the aerosat following re-entry, it would only need a small amount energy to replenish the envelope from leaks. With Venus being closer to the sun and thus having a higher solar flux, it would have plenty of power with solar energy.

Oxygen could be obtained from splitting CO2 in the same way a Mars base would do, or by breaking down sulphuric acid into its constituents using concentrated sun-light. Venus has about 3x times as much nitrogen than Earth, and could be mined using fractional distillation of liquefied atmosphere. Breaking sulfuric acid can release water vapor, and thus, a source for hydrogen. Materials that easily withstand corrosive H2SO4, and UV radiation do exist.

A Venus Cloud city has many advantages over space colonies; it would not require the “major engineering structures necessary to provide artificial gravity,” (well inside a gravity well) contain a breathable atmosphere from vacuum with “a high strength pressure vessel,” (ZERO pressure differential within and outside a cloud city envelope, vastly improving safety) and provide decent radiation protection without massive amounts of material shielding. (Though I do enjoy the many possibilities of artificial magnetospheres) 😉

In conclusion, floating Venus cities would offer a far more efficient use of asteroid material for a future, hopefully space faring humanity, and would provide a safer, healthier, and more spacious environment, just above another planet’s surface.